1. Field of the Invention
Present invention relates to a CVD (chemical vapor deposition) method for synthesizing diamond. A typical type of the CVD diamond is film. Here, we provide an apparatus and a method to synthesize powders typed diamond (several tens nm-several μm) with conventional CVD processes for deposition of diamond films. Gas phase nucleation has been induced on the boundary of the plasma generated normal CVD apparatus used for deposition of diamond films, and as a result the spherical diamond powders accumulated have been obtained on circumferences of the normal substrate.
2. Description of the Prior Art
Since diamond has the highest hardness among existing materials, diamond powder has been used as abrasive material added to polishing oil in order to improve an abrasive speed, in grinding an oxide group material and very hard material. A particle size of diamond powder used as abrasive material is in the range of several nm˜several tens μm. The particle size has a great influence on a surface roughness of ground material (abrasion object). In case of a lapping process regarded as rough abrasion having a surface unevenness as several tens μm, diamond powder having a size as several˜several tens μm is used. In case of abrasion for a hard surface having a surface unevenness as several tens nm, diamond powder having a size less than several μm is used.
In the conventional art, diamond powder as abrasive material is synthesized by breaking diamond having a size as several tens˜several hundreds μm, produced by i) an explosive method (diamond synthesis method using mixing gunpowder with solid graphite in a sealed container and exploding the mixture), or ii) a diamond powder synthesis method by a high pressure and high temperature (HPHT) method (diamond synthesis method using solid graphite as raw material and metal as catalyst at 1500° C. under 50,000 atmospheric pressure). However, diamond powder produced by the explosive method and the HPHT method has an irregular particle shape. It is not appropriate for grinding a hard surface so as to make it have a surface roughness less than several nm to use such diamond powder having an irregular particle shape as abrasive material, because the abrasion object may be scratched.
As a result, oxide group powder or metal powder is used at the end stage of polishing, instead of diamond powder. However, in this case, an additional abrasion process is added, and an abrasion speed lowers.
In order to solve these problems, inventors of the present invention synthesize spherical diamond powders accumulated by inducing gas phase nucleation in the CVD method).